Physicochemical and Microbiological Evaluation of Soil and Effluent Contaminated with Azo-Dye in Itoku, Abeoukuta Ogun State, Nigeria

Abstract

The global industrialization of chemical dyes used for household products has resulted in various dyes leaching into the soil. Azo dye textile contamination could lead to infertile soil. This study investigates the ecological effect of azo textile dye contamination on bacterial biomass, selective pressure, and associated physicochemical changes in soil samples contaminated with textile azo dye in Itoku, Abeokuta, Nigeria. Microbiological and physicochemical changes of the soil and effluent samples collected were determined using standard procedures.  Results revealed that the average count of total viable bacteria in the contaminated sampling sites ranged from 0.82±021 x 106 cfu/g to 1.65±0.02 x 106 cfu/g which was significantly lower than the control bacterial counts. The dye contaminated and the control soil samples each contained a heterogenous population of bacteria which included Paenibacillus validus, Bacillus licheniformis, Bacillus niacin, Seratia liquefaciens, Staphylococcus gallinarum, Bacillus subtilis, and Bacillus coagulans. The physicochemical analysis of the soil revealed high levels of pH in the azo dye contaminated soil (10.4–11.1) and electrical conductivity was also highest in the effluent (1250 to 2943 units) compared to the control (430 to 480).  Importantly, the control samples were higher in all of the other tested soil parameters including cation exchange, the mean value of the organic matter, water holding capacity, particle density, moisture content, and total porosity. Conclusion- Azo dye contamination caused decreases in bacterial density and many other soil parameters along with higher PH and electrical conductivity which suggests that azo textile dye contaminated soil is unfavorable for agricultural purposes and potentially toxic to the ecosystem.